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  1. 28 9月, 2021 1 次提交
  3. 14 7月, 2021 1 次提交
  5. 15 6月, 2021 1 次提交
    • M
      pid: take a reference when initializing `cad_pid` · 11774e84
      由 Mark Rutland 提交于 
      stable inclusion
from stable-5.10.43
commit 7178be006d495ffb741c329012da289b62dddfe6
bugzilla: 109284
CVE: NA

--------------------------------

commit 0711f0d7 upstream.

During boot, kernel_init_freeable() initializes `cad_pid` to the init
task's struct pid.  Later on, we may change `cad_pid` via a sysctl, and
when this happens proc_do_cad_pid() will increment the refcount on the
new pid via get_pid(), and will decrement the refcount on the old pid
via put_pid().  As we never called get_pid() when we initialized
`cad_pid`, we decrement a reference we never incremented, can therefore
free the init task's struct pid early.  As there can be dangling
references to the struct pid, we can later encounter a use-after-free
(e.g.  when delivering signals).

This was spotted when fuzzing v5.13-rc3 with Syzkaller, but seems to
have been around since the conversion of `cad_pid` to struct pid in
commit 9ec52099 ("[PATCH] replace cad_pid by a struct pid") from the
pre-KASAN stone age of v2.6.19.

Fix this by getting a reference to the init task's struct pid when we
assign it to `cad_pid`.

Full KASAN splat below.

   ==================================================================
   BUG: KASAN: use-after-free in ns_of_pid include/linux/pid.h:153 [inline]
   BUG: KASAN: use-after-free in task_active_pid_ns+0xc0/0xc8 kernel/pid.c:509
   Read of size 4 at addr ffff23794dda0004 by task syz-executor.0/273

   CPU: 1 PID: 273 Comm: syz-executor.0 Not tainted 5.12.0-00001-g9aef892b2d15 #1
   Hardware name: linux,dummy-virt (DT)
   Call trace:
    ns_of_pid include/linux/pid.h:153 [inline]
    task_active_pid_ns+0xc0/0xc8 kernel/pid.c:509
    do_notify_parent+0x308/0xe60 kernel/signal.c:1950
    exit_notify kernel/exit.c:682 [inline]
    do_exit+0x2334/0x2bd0 kernel/exit.c:845
    do_group_exit+0x108/0x2c8 kernel/exit.c:922
    get_signal+0x4e4/0x2a88 kernel/signal.c:2781
    do_signal arch/arm64/kernel/signal.c:882 [inline]
    do_notify_resume+0x300/0x970 arch/arm64/kernel/signal.c:936
    work_pending+0xc/0x2dc

   Allocated by task 0:
    slab_post_alloc_hook+0x50/0x5c0 mm/slab.h:516
    slab_alloc_node mm/slub.c:2907 [inline]
    slab_alloc mm/slub.c:2915 [inline]
    kmem_cache_alloc+0x1f4/0x4c0 mm/slub.c:2920
    alloc_pid+0xdc/0xc00 kernel/pid.c:180
    copy_process+0x2794/0x5e18 kernel/fork.c:2129
    kernel_clone+0x194/0x13c8 kernel/fork.c:2500
    kernel_thread+0xd4/0x110 kernel/fork.c:2552
    rest_init+0x44/0x4a0 init/main.c:687
    arch_call_rest_init+0x1c/0x28
    start_kernel+0x520/0x554 init/main.c:1064
    0x0

   Freed by task 270:
    slab_free_hook mm/slub.c:1562 [inline]
    slab_free_freelist_hook+0x98/0x260 mm/slub.c:1600
    slab_free mm/slub.c:3161 [inline]
    kmem_cache_free+0x224/0x8e0 mm/slub.c:3177
    put_pid.part.4+0xe0/0x1a8 kernel/pid.c:114
    put_pid+0x30/0x48 kernel/pid.c:109
    proc_do_cad_pid+0x190/0x1b0 kernel/sysctl.c:1401
    proc_sys_call_handler+0x338/0x4b0 fs/proc/proc_sysctl.c:591
    proc_sys_write+0x34/0x48 fs/proc/proc_sysctl.c:617
    call_write_iter include/linux/fs.h:1977 [inline]
    new_sync_write+0x3ac/0x510 fs/read_write.c:518
    vfs_write fs/read_write.c:605 [inline]
    vfs_write+0x9c4/0x1018 fs/read_write.c:585
    ksys_write+0x124/0x240 fs/read_write.c:658
    __do_sys_write fs/read_write.c:670 [inline]
    __se_sys_write fs/read_write.c:667 [inline]
    __arm64_sys_write+0x78/0xb0 fs/read_write.c:667
    __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]
    invoke_syscall arch/arm64/kernel/syscall.c:49 [inline]
    el0_svc_common.constprop.1+0x16c/0x388 arch/arm64/kernel/syscall.c:129
    do_el0_svc+0xf8/0x150 arch/arm64/kernel/syscall.c:168
    el0_svc+0x28/0x38 arch/arm64/kernel/entry-common.c:416
    el0_sync_handler+0x134/0x180 arch/arm64/kernel/entry-common.c:432
    el0_sync+0x154/0x180 arch/arm64/kernel/entry.S:701

   The buggy address belongs to the object at ffff23794dda0000
    which belongs to the cache pid of size 224
   The buggy address is located 4 bytes inside of
    224-byte region [ffff23794dda0000, ffff23794dda00e0)
   The buggy address belongs to the page:
   page:(____ptrval____) refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4dda0
   head:(____ptrval____) order:1 compound_mapcount:0
   flags: 0x3fffc0000010200(slab|head)
   raw: 03fffc0000010200 dead000000000100 dead000000000122 ffff23794d40d080
   raw: 0000000000000000 0000000000190019 00000001ffffffff 0000000000000000
   page dumped because: kasan: bad access detected

   Memory state around the buggy address:
    ffff23794dd9ff00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
    ffff23794dd9ff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
   >ffff23794dda0000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
    ffff23794dda0080: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
    ffff23794dda0100: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
   ==================================================================

Link: https://lkml.kernel.org/r/20210524172230.38715-1-mark.rutland@arm.com
Fixes: 9ec52099 ("[PATCH] replace cad_pid by a struct pid")
Signed-off-by: NMark Rutland <mark.rutland@arm.com>
Acked-by: NChristian Brauner <christian.brauner@ubuntu.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: Christian Brauner <christian@brauner.io>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Kees Cook <keescook@chromium.org
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
      11774e84
  7. 09 4月, 2021 1 次提交
  9. 08 4月, 2021 1 次提交
  11. 28 1月, 2021 1 次提交
  13. 07 1月, 2021 1 次提交
  15. 01 12月, 2020 1 次提交
  17. 13 11月, 2020 1 次提交
  19. 10 10月, 2020 1 次提交
  21. 19 9月, 2020 2 次提交
  23. 01 9月, 2020 1 次提交
  25. 08 8月, 2020 1 次提交
  27. 05 8月, 2020 2 次提交
  29. 31 7月, 2020 4 次提交
  31. 21 7月, 2020 1 次提交
  33. 16 6月, 2020 1 次提交
    • G
      security: allow using Clang's zero initialization for stack variables · f0fe00d4
      由 glider@google.com 提交于 
      In addition to -ftrivial-auto-var-init=pattern (used by
CONFIG_INIT_STACK_ALL now) Clang also supports zero initialization for
locals enabled by -ftrivial-auto-var-init=zero. The future of this flag
is still being debated (see https://bugs.llvm.org/show_bug.cgi?id=45497).
Right now it is guarded by another flag,
-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang,
which means it may not be supported by future Clang releases. Another
possible resolution is that -ftrivial-auto-var-init=zero will persist
(as certain users have already started depending on it), but the name
of the guard flag will change.

In the meantime, zero initialization has proven itself as a good
production mitigation measure against uninitialized locals. Unlike pattern
initialization, which has a higher chance of triggering existing bugs,
zero initialization provides safe defaults for strings, pointers, indexes,
and sizes. On the other hand, pattern initialization remains safer for
return values. Chrome OS and Android are moving to using zero
initialization for production builds.

Performance-wise, the difference between pattern and zero initialization
is usually negligible, although the generated code for zero
initialization is more compact.

This patch renames CONFIG_INIT_STACK_ALL to CONFIG_INIT_STACK_ALL_PATTERN
and introduces another config option, CONFIG_INIT_STACK_ALL_ZERO, that
enables zero initialization for locals if the corresponding flags are
supported by Clang.

Cc: Kees Cook <keescook@chromium.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NAlexander Potapenko <glider@google.com>
Link: https://lore.kernel.org/r/20200616083435.223038-1-glider@google.comReviewed-by: NMaciej Żenczykowski <maze@google.com>
Signed-off-by: NKees Cook <keescook@chromium.org>
      f0fe00d4
  35. 09 6月, 2020 1 次提交
    • V
      kernel/sysctl: support setting sysctl parameters from kernel command line · 3db978d4
      由 Vlastimil Babka 提交于 
      Patch series "support setting sysctl parameters from kernel command line", v3.

This series adds support for something that seems like many people
always wanted but nobody added it yet, so here's the ability to set
sysctl parameters via kernel command line options in the form of
sysctl.vm.something=1

The important part is Patch 1.  The second, not so important part is an
attempt to clean up legacy one-off parameters that do the same thing as
a sysctl.  I don't want to remove them completely for compatibility
reasons, but with generic sysctl support the idea is to remove the
one-off param handlers and treat the parameters as aliases for the
sysctl variants.

I have identified several parameters that mention sysctl counterparts in
Documentation/admin-guide/kernel-parameters.txt but there might be more.
The conversion also has varying level of success:

 - numa_zonelist_order is converted in Patch 2 together with adding the
   necessary infrastructure. It's easy as it doesn't really do anything
   but warn on deprecated value these days.

 - hung_task_panic is converted in Patch 3, but there's a downside that
   now it only accepts 0 and 1, while previously it was any integer
   value

 - nmi_watchdog maps to two sysctls nmi_watchdog and hardlockup_panic,
   so there's no straighforward conversion possible

 - traceoff_on_warning is a flag without value and it would be required
   to handle that somehow in the conversion infractructure, which seems
   pointless for a single flag

This patch (of 5):

A recently proposed patch to add vm_swappiness command line parameter in
addition to existing sysctl [1] made me wonder why we don't have a
general support for passing sysctl parameters via command line.

Googling found only somebody else wondering the same [2], but I haven't
found any prior discussion with reasons why not to do this.

Settings the vm_swappiness issue aside (the underlying issue might be
solved in a different way), quick search of kernel-parameters.txt shows
there are already some that exist as both sysctl and kernel parameter -
hung_task_panic, nmi_watchdog, numa_zonelist_order, traceoff_on_warning.

A general mechanism would remove the need to add more of those one-offs
and might be handy in situations where configuration by e.g.
/etc/sysctl.d/ is impractical.

Hence, this patch adds a new parse_args() pass that looks for parameters
prefixed by 'sysctl.' and tries to interpret them as writes to the
corresponding sys/ files using an temporary in-kernel procfs mount.
This mechanism was suggested by Eric W.  Biederman [3], as it handles
all dynamically registered sysctl tables, even though we don't handle
modular sysctls.  Errors due to e.g.  invalid parameter name or value
are reported in the kernel log.

The processing is hooked right before the init process is loaded, as
some handlers might be more complicated than simple setters and might
need some subsystems to be initialized.  At the moment the init process
can be started and eventually execute a process writing to /proc/sys/
then it should be also fine to do that from the kernel.

Sysctls registered later on module load time are not set by this
mechanism - it's expected that in such scenarios, setting sysctl values
from userspace is practical enough.

[1] https://lore.kernel.org/r/BL0PR02MB560167492CA4094C91589930E9FC0@BL0PR02MB5601.namprd02.prod.outlook.com/
[2] https://unix.stackexchange.com/questions/558802/how-to-set-sysctl-using-kernel-command-line-parameter
[3] https://lore.kernel.org/r/87bloj2skm.fsf@x220.int.ebiederm.org/Signed-off-by: NVlastimil Babka <vbabka@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: NLuis Chamberlain <mcgrof@kernel.org>
Reviewed-by: NMasami Hiramatsu <mhiramat@kernel.org>
Acked-by: NKees Cook <keescook@chromium.org>
Acked-by: NMichal Hocko <mhocko@suse.com>
Cc: Iurii Zaikin <yzaikin@google.com>
Cc: Ivan Teterevkov <ivan.teterevkov@nutanix.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: "Eric W . Biederman" <ebiederm@xmission.com>
Cc: "Guilherme G . Piccoli" <gpiccoli@canonical.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Link: http://lkml.kernel.org/r/20200427180433.7029-1-vbabka@suse.cz
Link: http://lkml.kernel.org/r/20200427180433.7029-2-vbabka@suse.czSigned-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      3db978d4
  37. 05 6月, 2020 1 次提交
    • C
      init: allow distribution configuration of default init · ada4ab7a
      由 Chris Down 提交于 
      Some init systems (eg.  systemd) have init at their own paths, for
example, /usr/lib/systemd/systemd.  A compatibility symlink to one of the
hardcoded init paths is provided by another package, usually named
something like systemd-sysvcompat or similar.

Currently distro maintainers who are hands-off on the bootloader are more
or less required to include those compatibility links as part of their
base distribution, because it's hard to migrate away from them since
there's a risk some users will not get the message to set init= on the
kernel command line appropriately.

Moreover, for distributions where the init system is something the
distribution itself is opinionated about (eg.  Arch, which has systemd in
the required `base` package), we could usually reasonably configure this
ahead of time when building the distribution kernel.  However, we
currently simply don't have any way to configure the kernel to do this.
Here's an example discussion where removing sysvcompat was discussed by
distro maintainers[0].

This patch adds a new Kconfig tunable, CONFIG_DEFAULT_INIT, which if set
is tried before the hardcoded fallback list.  So the order of precedence
is now thus:

1. init= on command line (on failure: panic)
2. CONFIG_DEFAULT_INIT (on failure: try #3)
3. Hardcoded fallback list (on failure: panic)

This new config parameter will allow distribution maintainers to move away
from these compatibility links safely, without having to worry that their
users might not have the right init=.

There are also two other benefits of this over having the distribution
maintain a symlink:

1. One of the value propositions over simply having distributions
   maintain a /sbin/init symlink via a package is that it also frees
   distributions which have a preferred default, but not mandatory, init
   system from having their package manager fight with their users for
   control of /{s,}bin/init.  Instead, the distribution simply makes
   their preference known in CONFIG_DEFAULT_INIT, and if the user
   installs another init system and uninstalls the default one they can
   still make use of /{s,}bin/init and friends for their own uses. This
   makes more cases Just Work(tm) without the user having to perform
   extra configuration via init=.

2. Since before this we don't know which path the distribution actually
   _intends_ to serve init from, we don't pr_err if it is simply
   missing, and usually will just silently put the user in a /bin/sh
   shell. Now that the distribution can make a declaration of intent, we
   can be more vocal when this init system fails to launch for any
   reason, even if it's simply because no file exists at that location,
   speeding up the palaver of init/mount dependency/etc debugging a bit.

[0]: https://lists.archlinux.org/pipermail/arch-dev-public/2019-January/029435.htmlSigned-off-by: NChris Down <chris@chrisdown.name>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Link: http://lkml.kernel.org/r/20200522160234.GA1487022@chrisdown.nameSigned-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      ada4ab7a
  39. 04 6月, 2020 1 次提交
    • D
      padata: initialize earlier · f1b192b1
      由 Daniel Jordan 提交于 
      padata will soon initialize the system's struct pages in parallel, so it
needs to be ready by page_alloc_init_late().

The error return from padata_driver_init() triggers an initcall warning,
so add a warning to padata_init() to avoid silent failure.
Signed-off-by: NDaniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Tested-by: NJosh Triplett <josh@joshtriplett.org>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Robert Elliott <elliott@hpe.com>
Cc: Shile Zhang <shile.zhang@linux.alibaba.com>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Steven Sistare <steven.sistare@oracle.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Link: http://lkml.kernel.org/r/20200527173608.2885243-3-daniel.m.jordan@oracle.comSigned-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      f1b192b1
  41. 15 5月, 2020 1 次提交
    • B
      x86: Fix early boot crash on gcc-10, third try · a9a3ed1e
      由 Borislav Petkov 提交于 
      ... or the odyssey of trying to disable the stack protector for the
function which generates the stack canary value.

The whole story started with Sergei reporting a boot crash with a kernel
built with gcc-10:

  Kernel panic — not syncing: stack-protector: Kernel stack is corrupted in: start_secondary
  CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.6.0-rc5—00235—gfffb08b3 #139
  Hardware name: Gigabyte Technology Co., Ltd. To be filled by O.E.M./H77M—D3H, BIOS F12 11/14/2013
  Call Trace:
    dump_stack
    panic
    ? start_secondary
    __stack_chk_fail
    start_secondary
    secondary_startup_64
  -—-[ end Kernel panic — not syncing: stack—protector: Kernel stack is corrupted in: start_secondary

This happens because gcc-10 tail-call optimizes the last function call
in start_secondary() - cpu_startup_entry() - and thus emits a stack
canary check which fails because the canary value changes after the
boot_init_stack_canary() call.

To fix that, the initial attempt was to mark the one function which
generates the stack canary with:

  __attribute__((optimize("-fno-stack-protector"))) ... start_secondary(void *unused)

however, using the optimize attribute doesn't work cumulatively
as the attribute does not add to but rather replaces previously
supplied optimization options - roughly all -fxxx options.

The key one among them being -fno-omit-frame-pointer and thus leading to
not present frame pointer - frame pointer which the kernel needs.

The next attempt to prevent compilers from tail-call optimizing
the last function call cpu_startup_entry(), shy of carving out
start_secondary() into a separate compilation unit and building it with
-fno-stack-protector, was to add an empty asm("").

This current solution was short and sweet, and reportedly, is supported
by both compilers but we didn't get very far this time: future (LTO?)
optimization passes could potentially eliminate this, which leads us
to the third attempt: having an actual memory barrier there which the
compiler cannot ignore or move around etc.

That should hold for a long time, but hey we said that about the other
two solutions too so...
Reported-by: NSergei Trofimovich <slyfox@gentoo.org>
Signed-off-by: NBorislav Petkov <bp@suse.de>
Tested-by: NKalle Valo <kvalo@codeaurora.org>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20200314164451.346497-1-slyfox@gentoo.org
      a9a3ed1e
  43. 12 5月, 2020 1 次提交
  45. 06 5月, 2020 1 次提交
  47. 11 4月, 2020 1 次提交
  49. 04 3月, 2020 1 次提交
  51. 21 2月, 2020 4 次提交
  53. 11 2月, 2020 1 次提交
  55. 06 2月, 2020 2 次提交
  57. 05 2月, 2020 1 次提交
  59. 01 2月, 2020 2 次提交
    • C
      init/main.c: fix misleading "This architecture does not have kernel memory protection" message · f596ded1
      由 Christophe Leroy 提交于 
      This message leads to thinking that memory protection is not implemented
for the said architecture, whereas absence of CONFIG_STRICT_KERNEL_RWX
only means that memory protection has not been selected at compile time.

Don't print this message when CONFIG_ARCH_HAS_STRICT_KERNEL_RWX is
selected by the architecture.  Instead, print "Kernel memory protection
not selected by kernel config."

Link: http://lkml.kernel.org/r/62477e446d9685459d4f27d193af6ff1bd69d55f.1578557581.git.christophe.leroy@c-s.frSigned-off-by: NChristophe Leroy <christophe.leroy@c-s.fr>
Acked-by: NKees Cook <keescook@chromium.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      f596ded1
    • A
      init/main.c: fix quoted value handling in unknown_bootoption · 283900e8
      由 Arvind Sankar 提交于 
      Patch series "init/main.c: minor cleanup/bugfix of envvar handling", v2.

unknown_bootoption passes unrecognized command line arguments to init as
either environment variables or arguments.  Some of the logic in the
function is broken for quoted command line arguments.

When an argument of the form param="value" is processed by parse_args
and passed to unknown_bootoption, the command line has

  param\0"value\0

with val pointing to the beginning of value.  The helper function
repair_env_string is then used to restore the '=' character that was
removed by parse_args, and strip the quotes off fully.  This results in

  param=value\0\0

and val ends up pointing to the 'a' instead of the 'v' in value.  This
bug was introduced when repair_env_string was refactored into a separate
function, and the decrement of val in repair_env_string became dead
code.

This causes two problems in unknown_bootoption in the two places where
the val pointer is used as a substitute for the length of param:

1. An argument of the form param=".value" is misinterpreted as a
   potential module parameter, with the result that it will not be
   placed in init's environment.

2. An argument of the form param="value" is checked to see if param is
   an existing environment variable that should be overwritten, but the
   comparison is off-by-one and compares 'param=v' instead of 'param='
   against the existing environment. So passing, for example,
   TERM="vt100" on the command line results in init being passed both
   TERM=linux and TERM=vt100 in its environment.

Patch 1 adds logging for the arguments and environment passed to init
and is independent of the rest: it can be dropped if this is
unnecessarily verbose.

Patch 2 removes repair_env_string from initcall parameter parsing in
do_initcall_level, as that uses a separate copy of the command line now
and the repairing is no longer necessary.

Patch 3 fixes the bug in unknown_bootoption by recording the length of
param explicitly instead of implying it from val-param.

This patch (of 3):

Commit a99cd112 ("init: fix bug where environment vars can't be
passed via boot args") introduced two minor bugs in unknown_bootoption
by factoring out the quoted value handling into a separate function.

When value is quoted, repair_env_string will move the value up 1 byte to
strip the quotes, so val in unknown_bootoption no longer points to the
actual location of the value.

The result is that an argument of the form param=".value" is mistakenly
treated as a potential module parameter and is not placed in init's
environment, and an argument of the form param="value" can result in a
duplicate environment variable: eg TERM="vt100" on the command line will
result in both TERM=linux and TERM=vt100 being placed into init's
environment.

Fix this by recording the length of the param before calling
repair_env_string instead of relying on val.

Link: http://lkml.kernel.org/r/20191212180023.24339-4-nivedita@alum.mit.eduSigned-off-by: NArvind Sankar <nivedita@alum.mit.edu>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Krzysztof Mazur <krzysiek@podlesie.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      283900e8